On April 5th, Bill Hylander (http://today.duke.edu/2010/04/hylander.html),
delighted an inquisitive group of high school students with a careful
description of primate history. Bill’s
focus was placed upon the evolution of jaw bones and cranial structure, (his
expertise), and he brought with him several models of skulls. His approach was sensitive to the fossil
evidence, and how we know what we know.

Understanding the biology of us, and all the other living
things with which we share a genetic past, was emphasized by his discussion of
the historic splitting where and when. Divergence
was best demonstrated by his discussion on chimpanzees, with whom we 'parted'
long ago. Humans are not in direct
lineage with chimpanzees, though chimps and humans do share a common
ancestor.

The tree of species evolution is full of branches and offshoots,
most of which have been dead ends. Species living today can be
traced all the way back to the first life forms on the planet. Every living
individual has an ancestor that is so closely related that it is
indistinguishable from its next nearest ancestor and successor. But...when you
look at a really long time line, like tens of thousands of generations, there
are definite differences. Bill shared an illustrative idea of stacked
pictures with a snap shot of any of us on the top and our great (to the
millionth) grandmother at the bottom. Every picture looks like the others
on each side, but carried to this extreme, the differences are huge and the
bottom picture is likely a fish.
Bill pointed out that the life forms existing today share common ancestors, but
are not descendants of other forms also existing today. We and chimps are
on the tips of our respective branches and have a common ancestor back at the
last fork, for example, but we did not evolve from chimps. We are each ends
of a different branch of the evolutionary tree.

An important aspect of Bill’s presentation was the hands-on
experience with the skull models. Many
students had good questions, which Bill entertained for another half hour.